Summary of Significant Accounting Policies (Narrative) (Details) $ in Thousands		3 Months Ended								12 Months Ended
	Apr. 23, 2019 USD ($) lot	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jan. 01, 2018 USD ($)	Mar. 31, 2017 USD ($)	Jan. 01, 2017 USD ($)
Operating Lease, Liability		$ 70,029								$ 70,029
Finite-Lived Intangible Assets, Net		84,600				$ 86,800				84,600	$ 86,800
Unfunded settlements		6,200				40,900				6,200	40,900
Restricted Cash and Cash Equivalents		33,543				23,612				33,543	23,612
Intangible assets, accumulated amortization		204,400				190,200				204,400	190,200
Intangible assets amortization expense										14,200	13,800	$ 13,800
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months		14,400								14,400
Future Amortization Expense, Year Two		11,000								11,000
Future Amortization Expense, Year Three		6,300								6,300
Future Amortization Expense, Year Four		6,250								6,250
Future Amortization Expense, Year Five		6,250								6,250
Property and equipment, net		111,713				92,935				111,713	92,935
Property and equipment, accumulated depreciation		$ 218,900				209,300				218,900	209,300
Depreciation Expense										39,800	35,600	37,200
Advertising Expense										53,900	51,000	45,000
Employee benefit plan company contributions										$ 19,100	17,900	15,700
Number of VIEs requiring consolidation		0								0
Residential mortgage loans available-for-sale		$ 508,967				461,354				$ 508,967	461,354
Residential mortgage loans available-for-sale aggregate outstanding principal balance		494,100				444,200				494,100	444,200
Net gain (loss) from change in fair value										(600)	700
Net gains from the sale of mortgages										$ 129,400	111,300	110,900
Days past contractual term once loans no longer accrue interest income										90 days
Variability in future cash flows of derivative instruments in days										60 days
Cumulative Effect of New Accounting Principle in Period of Adoption													$ 22,411		$ 18,238
Income Tax Expense (Benefit)		(100,153)	$ (93,042)	$ (79,735)	$ (49,946)	(91,842)	$ (95,153)	$ (85,081)	$ (53,440)	$ (322,876)	(325,517)	(491,607)
Contract liabilities		294,400				254,600				294,400	254,600
Revenue from Contract with Customer, Excluding Assessed Tax										10,212,957	10,188,331	8,577,686
Capitalized contract costs		35,100				30,800				$ 35,100	30,800
Contract assets													27,700
Minimum | Office Furniture and Equipment [Member]
Property and equipment, useful life										3 years
Minimum | Software and Hardware [Member]
Property and equipment, useful life										3 years
Minimum | Model Park Improvements and Furnishings [Member]
Property and equipment, useful life										1 year
Maximum | Office Furniture and Equipment [Member]
Property and equipment, useful life										10 years
Maximum | Software and Hardware [Member]
Property and equipment, useful life										5 years
Maximum | Model Park Improvements and Furnishings [Member]
Property and equipment, useful life										5 years
Financial Services [Member]
Interest income on mortgage loans										$ 9,700	11,300	9,500
Interest Rate Lock Commitments [Member]
Derivative, Notional Amount		255,300				285,000				255,300	285,000
Forward Contracts [Member]
Derivative, Notional Amount		518,200				511,000				518,200	511,000
Whole Loan Commitments [Member]
Derivative, Notional Amount		$ 200,700				$ 187,800				$ 200,700	$ 187,800
American West Homes [Member] [Member]
Business Combination, Consideration Transferred	$ 163,700
Number of Units in Real Estate Property | lot	1,200
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	$ 12,000
Intangible asset useful life	20 years
American West Homes [Member] [Member] | Land Option Contracts [Member]
Number of Units in Real Estate Property | lot	2,300
JW Homes (Wieland) [Member]
Goodwill														$ 40,400
Restricted stock [Member]
Share-based compensation vesting period										3 years
Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption													22,411		18,644
Accounting Standards Update 2016-09 [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption															$ 18,600
Income Tax Expense (Benefit)												$ 7,700
Accounting Standards Update 2014-09 [Member] | Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption													$ 22,400